New Best Solutions for the Close-Open Mixed Vehicle Routing Problem by using an Improved Harmony Search Algorithm

This paper addresses the close-open mixed vehicle routing problem (COMVRP) that both close and open variants of the vehicle routing problem are simultaneously considered. The objective is to find the solution which minimizes the total cost of delivery. In this paper, we propose an improved harmony search algorithm (IHSA) composed of two main approaches. First, the probabilistic Clarke-Wright savings algorithm is applied to improve an initial COMVRP solution. Second, that solution is used to produce the best COMVRP solution by the music improvisation process. The computational results on well-known benchmark problems show that the IHSA is superior to the best existing algorithm. Moreover, new best solutions for 10 benchmark instances are also found.